Resistive random access memories (RRAMs) are non-volatile memory devices that utilize a change in resistance characteristics of so-called “variable resistance materials” to store data. Such variable resistance materials (e.g., transition metal oxides or phase change materials) have a resistance that changes relatively significantly at a particular voltage. When a particular voltage is applied to the variable resistance material, the resistance of the variable resistance material decreases, which is referred to as a so-called “on” state. When a reset voltage is applied to the variable resistance material, the resistance of the variable resistance material increases, which is referred to as a so-called “off” state. Among conventional RRAMs, a cross-point RRAM has a relatively simple cell structure and relatively high density.
A conventional cross-point RRAM includes a plurality of substantially parallel word lines and a plurality of substantially parallel bit lines, the bit lines arranged substantially perpendicular to the word lines. A so-called “cross-point” is formed at the intersection of the word lines and bit lines. A memory resistor is disposed between the word lines and bit lines at each cross-point. The memory resistor may have a multi-layered structure including, for example, a layer including a memory element and at least one layer including a non-ohmic device (e.g., a metal-insulator-metal (MIM) device).
Cross-point memory architecture provides high device density, yet it suffers from substantial leakage current, which may result in increased power dissipation and a reduced sensing margin. Parasitic resistance associated with conductive lines (i.e., word lines and bit lines) may result in degradation of output signal and restrictions on array size.